The portions of an individual that could benefit from orthotics are many, and come in many different sizes and shapes. Even the same portion of different individuals, such as the foot, come in many different sizes and shapes, and need different corrections, so that the more customized an orthotic appliance/orthosis is, the more the orthotic appliance/orthosis will benefit the individual.
Making custom orthotics requires extensive training and hand-on experience. Even after that training and experience is gained, the current processes for creating orthotics is very time consuming and is as much art as science. The process involves many steps, such as examining the foot, casting the foot to create a negative impression, pouring plaster inside the negative (to create the positive mold that the orthotic is eventually fabricated from), fine tuning the shape of the plaster positive, vacuum forming plastic and/or rubber to create the orthotic shell, posting (gluing extra material) to the heel and base to prevent rocking, and grinding the posting flat and smoothing the finish. It takes about two hours to make an orthotic using the plaster casting method.
Making a custom orthotic appliance/orthosis using the plaster casting method can be expensive. Making an orthotic appliance/orthosis which is not custom, and just uses off-the-shelf standard components, is less expensive, but often results in an orthotic appliance/orthosis which provides much less of a benefit.